As a conventional LED dimming apparatus, the one described in Patent Literature 1 (Japanese Patent Laid-Open Publication No. 2003-157986) has been known. This conventional LED dimming apparatus implements control for a voltage applied to an LED and switch dimming of the LED by a switching element that flows and interrupts an LED current in combination with each other. This LED dimming apparatus receives an external dimming signal by a control circuit. When a dimming degree that is based on the dimming signal is low (when emitted light is bright), the LED dimming apparatus constantly maintains the applied voltage to the LED, and dims the light by changing an ON/OFF duty ratio of the switching element. When the dimming degree that is based on the dimming signal is high (when the light is dark), the LED dimming apparatus constantly maintains the ON/OFF duty ratio of the switching element, and dims the light by changing the applied voltage to the LED.
In the case where the applied voltage to the LED is maintained constantly, and the light is dimmed by changing the ON/OFF duty ratio of the switching element, it is necessary to set an ON/OFF frequency of the switching element to be high so that the light from the LED cannot look flickering. Meanwhile, when the dimming degree is high (when the emitted light is dark), an ON-time of the switching element is shortened. In particular, at the time of such light dimming in which the duty ratio is nearly 0%, it is difficult to control the ON-time of the switching element with high accuracy. Therefore, in a low duty-ratio range where the ON-time of the switching element can be controlled with high accuracy, the switch dimming to turn on/off the switching element is performed. At the time of the light dimming when the dimming degree is higher than in the low duty-ratio range where the ON-time of the switching element can be controlled with high accuracy, the ON-time of the switching element is maintained constantly, and the light dimming in which the applied voltage to the LED is changed is performed. In such a way, it becomes possible to perform the light dimming to a higher dimming level in proportion to the dimming signal.